Gov.uk has posted "Essential maintenance to our online services: Maintenance from 8am to 8pm on Saturday 23 January will affect confirmation receipts for online filing.
It might take longer to get your confirmation receipt if you file online between 8am to 8pm on Saturday 23 January. This includes software filing.
Any disruption will be minimal and our online services are available to use as normal. We’re sorry for any inconvenience."
Having checked with HMRC, this does not apply to HMRC online services, but comes from Companies House – will this cause trouble?